User Equipments (UE) for communication are also known as e.g., wireless devices, terminals, mobile terminals, wireless terminals and/or mobile stations. UEs are enabled to communicate wirelessly in a cellular communications network or wireless communication system, sometimes also referred to as a cellular radio system or cellular networks. The communication may be performed e.g. between two UEs, between a UE and a regular telephone and/or between a UE and a server, such as server providing video streaming service, via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the cellular communications network.
UEs may further be referred to as mobile telephones, cellular telephones, computers, or tablets with wireless capability, just to mention some further examples. The UEs in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another UE or a server.
A cellular communications network covers a geographical area which is divided into cell areas, mostly overlapping each other, wherein each cell area is served by a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. eNodeB (eNB), NodeB, B node, Base Transceiver Station (BTS), or AP (Access Point), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the UEs within range of the base stations. The base stations and the UEs involved in communication may also be referred to as transmitter-receiver pairs, where the respective transmitter and receiver in a pair may refer to a base station or a UE, depending on the direction of the communication. Two UEs involved in D2D communication may also be referred to as a transmitter-receiver pair. In the context of this disclosure, the expression Downlink (DL) is used for the transmission path from the base station to a UE. The expression Uplink (UL) is used for the transmission path in the opposite direction i.e. from the UE to the base station.
Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for communication with terminals. The 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies.
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks.
3GPP LTE radio access standard has been written in order to support high bitrates and low latency both for uplink and downlink traffic. The data transmissions in LTE are controlled by the radio base station.
Indoor utilization of wireless cellular technology is emerging, and with this development, indoor specific deployments increase to meet network capacity and expectations of end user experience.
It will therefore be of emerging interest to know if a cellular user such as e.g. a UE, in fact is located indoors or outdoors. A network may try to find out if the UE is located indoors is by using positioning services, and more specifically in context of emergency matters. In public safety and emergency scenarios, it would be beneficial to gain better knowledge on e.g. in which building and in which floor a specific UE is located, to be able to warn the user of the UE by notification or call if the user of the UE is unknowable in danger, or the other way around if the UE is making an emergency call it is important to identify if the UE is inside a building to be able to send help.
Other areas of application may for example be network optimization algorithms and tuning where it is of interest to know if a UE is inside or outside a specific building, so that a base station may consider the indoor/outdoor classification in the radio resource management to improve the user experience of the UE. For example, indoor UEs may be assumed to be subject to specific mobility behavior, or may be requested to start monitoring indoor cells on a dedicated frequency carrier.
Unfortunately, indoor GPS positioning is often very inaccurate or even impossible. Some indoor radio systems with very high density of cells, such as e.g. Radio-Frequency Identification (RFID) which is a wireless use of electromagnetic fields to transfer data or similar, for the purposes of automatically identifying and tracking tags attached to objects, may possibly deduct a more accurate user location, but such systems are still very rare. RFID is a short range radio tags solution.
Other possible solutions are Inertial Navigation Systems (INS), with or without GPS support. An INS is a navigation aid that uses a computer, motion sensors and rotation sensors to continuously calculate e.g. the position of a moving object without the need for external references. However, so far none of these solutions is practically feasible for cellular UEs of today.